[PATCH] GlobalOpt enhancement optimization (hoisting of initialization code into constant global initializers).

[Puyan Lotfi]

All:

Attached is a patch to GlobalOpt that adds an optimization that takes user written constant initialization code for global variables and hoists the initialization values into the global initializer. This optimization is only done on locally linked globals of integral types (scalars, arrays, and structs) that are constant initialized (and zero initialized prior to transformation). 

The idea is to transform the following code:

A = internal global i32 0, align 4
isInit = internal global i1 false

define i32* foobar() {
  %.b = load i1* isInit
  %1 = zext i1 %.b to i8
  %2 = trunc i8 %1 to i1
  br i1 %2, BB4, label BB3
BB3:
  store i32 113, i32* A, align 4
  store i1 true, i1* isInit
  br label %4
BB4:
  ret i32* A
}

Into:

A = internal global i32 113, align 4

define i32* @_Z8initTestv() {
  ret i32* A
}

Could someone on the list review my changes, provide feedback, and if possible submit my changes?

I also have some test cases I've written but I am still trying to figure out how to add them to llvm/test/Transforms/GlobalOpt (I don't see a lit.local.cfg in that directory as the docs specify). 

Thanks

-Puyan


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